Hardboard having a paper overlay bonded thereto with a drying oil using a boron trifluoride catalyst



United States O This invention relates to a process for making artificial board, and to the product of such process, and more parice Patented Jan. 31', 1967 specification and claims, this may include the ether or the phenol complex.

I The amount of boron trifiuoride or other Friedel-Crafts type catalyst can be varied within rather wide limits, preferably about two to ten percent.

The nature of this invention will additionally be ap parent from the examples that follow. All of the boards used in the tests described below had a newsprint paper ticularly relates to artificial boards comprising a hardboard base mat having a paper overlay in which a drying oil, in a polymerization catalyst is incorporated, provides gust of the bond between the base mat and the overlay.

A barrftoard having a paper overlay can be made by the met o described in Canadian Patent 537,683 dated March 5. 57, for an invention by Dorland et al. entitled Arti..-ciz.l Board To Provide a Hardboard Having a Sheet of Paper lzregrally United with the Surface of the Hardboard, Canadian patent corresponding to US. Patent l ce Z.9l8,398.. A drying oil, such as linseed oil, is usually used to supplement the bonding due to the lignins, herticelluloscs and other natural bonding constituent of the ulp. A and hnrd'zwwxi mat, to r with the e2; 5 oil, are *t; .ssed, and then the boards are baked to complete the polymerization of the drying oil. The overlay sheet can be coated in the manner desc ibed by Canadian Application 759,049, filed Septembe 1958, and entitled Improvement in Hardboard Ove'a corresponding to Dorland et al. US. Pat ent No. 33,579. The paper overlay frequently has wood grain patterns printed on it.

During manufacture of artificial board of the type referred to above, there are a number of rejects resulting from deli-es such as edge tear, edge peel, or the lifting or separatbn of the overlay paper from the mat in cer tain spots As most of these defect appear at the time of press egening, they cannot readily be remedied. it is believed nut these defects are due to a lack of adhesion between the overlay paper and the board mat during the It has been found in ac ordance with this invention that the frregoing can be achieved by incorporating in the drying o? a Friedel-Cratts type catalyst. A particularly effective isprovcment has been obtained by the use of boron trifisoride.

\"arior s 'sriedchcrafts type catalysts may be used, including the halides of aluminium, tin. titanium, antimony, zine, iron and boron, such as boron trifi'uoride, aluminum trichioride. and stnnnic tetrachloride. As previously indicated. Barron tritiuoride is particularly eflective, as will become apparent from the examples which follow. Aluminurn trizitioride and stannic tetrachloride show a signifieant improvement in bond strength, but the overlay papet is has discoloured and the post-bake washability is im aired. The boron triuoride may be used in the form of one of its complexes, such as the ether or the phenol complex and it will be understood, unless otherwise indicated, slat. where boron tritiuoride is specified in the seconds.

v overlay on one surface.

The mat was made from a fumish consisting of a 50:50 mixture of softwood and hardwood fibres, employing a defibration technique which, in its essentials, followed the well-known Asplund procedure.

The following procedure was used: approximately 2300 g.

(on a moisture-free basis) of fibre is slushed with approximatcly 330 lbs. of water. The pH of the water is adjusted to 5.5 with sulphuric acid. A phenolic based binder in an amount equivalent to 0.85% and a wax size in the amount of 0.75 $2 of the moisture-free weight of the fibres are then added to the mixture. The mixture is stirred for about 15 minutes, after which 0.3% (based on the moisture-free fibre weight) of alum is added. The pH is adjusted to 4.5 with sulphuric acid and the stirring continued for a further period 0f 15 minutes. A 2 it. x 2 it. mat is then formed and cold pressed.

The overlay sheets are prepared by cutting large sheets into the proper size (I it. x l ."as tour overlays are ualfy place i on laoo made eqerimental boards), and spraying the adhes e oil on the unprinted side of the overlay by means of a spray gun. The amount (i) From 0 to 400 p.s.i.g.in 35 seconds. (2) At 400 p.s.i.g.for 5 seconds.

(3) From 400 psig to p.s.i.g.--in 15 seconds. (4) At 100 p.s.i.g.-ior 12 minutes, 35 seconds. Total timel3 minutes, 30 seconds. I Q

Where a total press time of ll minutes is used, the time at p.s.i.g. (stage 4) is reduced to 30 minutes and 5 After hot pressing, the boards are baked in an oven at a temperature between 250 F.300 F. for a period of 3 to 5 hours. In the present series of experiments, the baking was carried out in a drought oven for 4% hours at 250 F. in all instances. During pressing, however, two press plate temperatures, 325 F. and 350 F., were used.

The boron trifiuoride oil was accomplished by adding the specified quantity of the boron tritluoride complex to the oil, followed by gentle stirring.

The sulphurized oils were prepared by adding the requisite amount of flowers of sulphur to a known amount of linseed oil and gently heating the mixture to 180 C. in about an hour. When the temperature reached 180 C., the oil started to froth, and the heating was stopped. The sulphurized oils were very viscous and were of a dark colour. Owing to the high viscosity of the sulphurizcd oils, they could not be sprayed and were brushed on the overlay.

s A; A l

' The maleinized oil maleic anhydride content To 200 C in 1 hour.

At 200 C.220 C.for 1% hours.

To 250 C.in.l% hours.

At 240 C.-250 C.-for hour.

The maleinized linseed was also quite viscous and had to be brushed on the overlay sheets.

Baking in an atmosphere of nitrogen was accomplished by placing 3 in. x 6 in. strips of the unbaked board in a stainless steel bomb (8 in. diameter and 1 ft. in length) provided with inlet and outlet valves and a pressure gauge. After the board strips were in position, the bomb was filled with nitrogen, after flushing out the air in the bomb by a stream of nitrogen for about minutes. The bomb was then placed in a draught oven and heated for 4.5 hours at 250 F.

The paper (overlay) hardboards were submitted to four different tests in order to evaluate the strength of adhesion (and its water-resistance) and the surface properties of the overlay. These tests were:

(1 Out-of-press dry break tear test.

(2) Post-bake boil test.

( 3) Post-bake washability tes (4) Post-bake wax test.

The details of the tests are given below:

(1) Out-oj-prcsr dry break tear lesL-As its name implies, this test was performed on the boards prior to baking with a minimum of time lag between press release and the performance of the test. In all instances, the tests were perforated within two minutes of press release.

For the test. the board was cut in 12 in. x l in. strips and the strips were sharply broken in the middle by hand, with the line of fracture perpendicular to the length of the strips. The fracture was initiated on the non-overlay side of the strip. and as the fracture reached the overlay, the two newly-formed strips were sharply pulled away from each other. This resulted in the overlay being peeled off the surface of the strips to a greater or less extent. The extent of the peel was a measure of the strength of the out-of-press overlay bond, being inversely proportional to it.

(2) Post-bake boil test.This test'was designed primarily to measure the water-resistance of the overlay bond, but it also furnishes a measure for the bond-strength under the conditions of the test. The test is usually performed on samples of the baked board.

For this test, the board was cut into small squares l in.

x 1 in.), and the squares put into a beaker of boiling distilled water and the boiling was allowed to continue for one hour. Six to twelve small squares were used for each test. After one hour, the squares were picked up and an attempt was made manually to peel the overlay ofi the surface of the squares, without disturbing the base board. The portion of the total area or the square exposed was estimated and reported as the boil test peel value]? expressing it as a percentage of the total area. The higher the boil test peel value, the lower was the water-resistance of the overlay bond.

(3) Post-bake washabiliry test.This test measures the surface toughness of the finished woodgrain (overlay) hardboard, and was conducted using a Gardner Staight Line Washability Tester. The procedural details may be found in "Physical and Chemical Examination of Paints,

varnishes. Lacquers, and Colours by H. A. Gardner and G. G. Sward (p. 3968). (The hook is distributed by H. A. Gardner Laboratory, Inc., Bethesda, Maryland, USA.) A strip of the board is given 3000 scrubs by a mechanical brush in the presence of distilled water. If the surface of the board surfers no visible damage after 3000 scrubs, the board is rated as having a satisfactory degree of washability.

(4) Pick wax rest for surface strengIh.This test was performed on the baked board, and the procedure adopted was, in its essential aspects, the same as that recommented by TAPPl (Technical Association of the Pulp and Paper Industry) in standard method T4S9m-48.

in this test, a series of hard-resin, non-oily waxes is used, numbered in an ascending order in accordance with their adhesive strength. Thus each wax in the series is progressively more adhesive than the next lower one in the numerical order. The wax sticks used in the test were the same as recommended in TAPPl standard method T459m-48.

To carry out the test, the wax sticks were melted under a Bunsen flame at one end. and then placed firmly on the surface of the board. After the wax had cooled to room temperature, the stick was sharply pulled away from the board, the direction of pull being at right angles to the board surface. The highest numbered stick which broken away clean without leaving any surface damage) from the surface was quoted as the wax number of the board.

The results obtained are set forth in Tables I, II and III herein.

TABLE L-BOARDS tmzssan AT 325 F.

- Post Baku Experiment Type of Overlay Adhesive Used Total Press Out-ot-Pmss Baking Conditions lloii Post Post Bake Post Bake Time, )ltn. BrcnklTcar Peel, Percent \las .s'o. Washability 1 Linseed Oil 13. 5 4.5 hrs. at 250 F-- 2 do 13. 5 .do 25-50 Exmllcnt. 3 13 5 30-70 Do. 4 l3. 5 540 2'5 Do. 13. 5 10-20 25 D0. 13. 5 15-10 m D0. 13. 5 10-20 l3. 5 I540 13. 5 20-50 13, 5 10-20 l3. 5 15-10 26 D0. d 23. 5 25-50 25 D0. 13 linseed plus 5% BF; Ether- I3. 5 15-40 3 Do. 14 Linseed plus 10% BF; Ether l3. 5 0-5 Do. 1 5 l3. 5 0-5 26 Do. d9 13. 5 0-5 26 D0. 13. 5 05 26 Do. .do 13. 5 0-5 35 D0.

DCO plus 3% BF; Ethe 13. 5 DCO plus 5% BF: Elite 13. 5 0-5 25 Do. do 13. 5 0-5 26 Do. do 13 5 Prowler t 0-5 26 D0.

Rating of Outolres Break 'lear Test:

1. Very poor. Total peel. 2. Good. length of peel less than 3 111..

3. Very good. Length of peel les than 2th. 4. Excellent. Length of peel less than $5 in.

TABLE IL-BOARDS PRESSED AT 350' F.

Post Bake '2" Experiment i Type 01 Overlay Adhesive Used Total Puss Ont-oi-Iress Baking Conditions Boil Test Post Bake Post Duke 1 Nut. Time, Min. Break/Tear Peel, Peroent Wax No. washabrlrty I Linseed oil 13. 5 4.5 hrs. at 250 F... 50-70 i 50:50 mixture of lung and linseed 13.5 dn -20 110.-.. 13. 5 -25 v 1 do 13. 5 5-2] 23 Exfiellent. L 13. 5 5-30 25 D0. Z 13.5 15-30 26 D0. 13.5 10-25 26 13.5 0-5 26 Do. 13. 5 0-5 26 D0. 13. 5 0-5 26 D0. 13. 5 0-5 D0.

13. 5 0-5 26 D0. 5 13. 5 0-5 26 Do. 13. 5 0-5 26 Do. 13. 5 0-5 26 D0. 13. 5 0-5 25 D0. 13; 5 0-5 11- 5 0-5 11.5 0-5 v 13. 5 0-5 v D0. 13. 5 0-5 D0. 1 l3. 5 0-5 25 Do. 13. 5 0-5 '1 13.5 0-5 13. 5 0-5 s 11 10-20 11 10-15 23 135.; V .do 11 10-20 21 Do. :50 mix! um 01' iung and li 11 10-20 26 Do. emulsified with equal amuunt of water. 3I o 11 d0 d0 10-20 26 Do. Linseed oil crnulsifiQ with equal 11 our -.clo 10-25 26 Do.

amount oi \vezer. 33. .do 11 10-25 3-1- Cnitol BX 11 100 w 50: 50 mixture 01 Unrtol BX and 11 -100 '1 linseed. 3T An 11 Poor 610-..-.. 00-100 18 3\ 50:50 mixture 01 Unitol BX and 11 Do.

E linseed plus 10% B1; Ether. 39 1 d0 11 D0. 10 Linseed plus 10% sulphur 11 1- Linseed pl "2 sulphus 11 -11 Linseed plus sulphur 11 43 1 Mnleic Linseed 13.5 44 3 Zymul. 11 .1 45. may 11 h Zynwl, thinned with solvent 11 7 vcu'suy, thinned with solvent.-. 11 0: Maleic linseed plus 4% BF; Ether 5 Q Q3 31 11 l a 11 31 :T 11

3 do 11 .-do-. i 5-.L .do 11 i 0 s5 Commercially bodied linseed thinned 11 -.do--. 00-70 1; with solvent. E6 Linseed plus 50 11 .110. 60-80 57 :50 mixture of t g and linseed 13. 5 .110. 211-60 plus 0.1% Fe drier. 1- 5 DCG plus 0.1% Fe drier 13. 5 (in do 20-00 DC Oflus 0.05% Cudriex' plus 0.3% 13. 5 do Pb ric-r. D511) 1115 0.10% (Io-drier plus 0.6% 13. 5 da de 1 ru-r. f erz Linseed plus 10% A101 11 Good .do 0-5 18 Poor. 6L Linseed plus 10% SnCl; 11 do 0-5 18 Do.

Ratiuzgsf mi-Press Breakl'iear Test: 1 1- vie E'uOr. Total peel. 4. Good. Length of peel less than 3 in. 1'... I Length of peel between 4 in. and Gin. 5. Very good. Length 01 peel less than 2111.

3 fair. Length of peel between 4 111. and 8 in. 6. Excellent. Length of peel less than A in.

TABLE III.-BOARDS PRESSED AT 350' F.

. Post g Total Bake Post Exper'mi Type of Overlay Adhesive Used Aging time Press Out-oi-Press Baking Conditions Boil Bake Post Bake K v 01 Adhesives Time, Break/Tear Test Wax Wuslmbility Y 7 Min. Peel, N o.

- I Pennant Linseed plus 5; BF; 2 thei 11 Excellent 45 hrs. at M F.. 0-5 26 Enemy 1; Linseed plus 10% B1; Ether 11 ..d0 do 0-5 26 DB, a." -d 11 0-5 26 Do. 4 i 11 0-5 25 DO, 5 11 0-5 M Do. 5. 11 0-5 26 Do. 7 11 0-5 26 Do, 5 d0 11 (10..... 0-5 26 Du.

' 50:50 mixture of mug and linseed. 11 4.5 hrs. at 250 F1. 18 DCO 11 do. 100 DCO plus 7% BF; Ether 11 -do. 19-30 finds zfimgen.

' v 7 The rasnlts'given' in Table I, which refers to boards pressed with a press plate temperature of 325 F., show that WllfiZi linseed oil, a 50:50 mixture of tung oil and linseed oil, or pure tung oil was used as the overlay adhesive,

the ODI- Di-PIEF... bond was poor. The break tear test lower than the values obtained with uncatalyzed oils (Expet-intents l-lZ). The wax pick test, in general, yielded values as as 26 for both catalyzed and uncatalyzed oils. As values exceeding 18 are generally considered satisfactcay for woograin hardboards, the results were considered excellent. The washability test also showed excellent (Le. board surface was unmarred) in every inszance both with and without the catalyst. Thus catalysis BF; was shown to have no ill effects on the surface toughness of woodgrain boards, as measured by the was: pick or thwashability tests.

Experiment 13 needs a special comment. In this instance, tine amount of catalyst. used was 5% and the oil was linseed. it will be noticed that, in this experiment, the out-oz pres break tear showed a peel length between 2-3 inches and a post-bake boil test peel value in the range 15-40%. While the break tear" was much superior to nnczzzlyzcd oil boards, the boil test" values were not impressed. This brought out the fact that when the press plate temperature is kept low (325 F. instead of the usszl 350 F.), the catalyst concentration should be maintained a: a level higher than 5% in order to obtain the best results.

The dzca in Table II (which refer to boards pressed at 350 15.} amply confirm the data presented in Table I. In the inseam where oils with no catalysts were used (Experiments l-7), the out-of-press break tear tests" showed a rating of very poor (total peel). The "bo test values were, in general, in the range 1020% occasional lower and higher values.

Expert-hens 8 to 12 list the results obtained with linseed oil plus 5% BF -ether. The out-of-press break tear vaines were either very good" (length of peel less than 2 imies) or excellent (length of peel less than A inch). The Soil test values were consistently below 5%.

Experiments 3 to 20 show the results of increasing the catalyst enumeration to 10%, still using linseed oil. The bf-fl; me was uniformly excellent and boil values were below 5% in all instances.

Experimen s 21 to 26 show the results of using BF;- phenol complex a the catalyst rather than the ether complex. These esrgeriments showed that the phenol complex was also an er'zective catalyst for the promotion of bonding char'azzeristics in linseed oil.

Experimen s 27 to 29 used soya oil which is a semidrying or? having rather poor air-drying characteristics. The CHL'LIKSZ used was BF -ether in 10% concentration. The showed that the break tear was almost as good as that obtained with linseed plus 10% BF -ether. The bot? tesz peel value hovered around 10-20%, a range as that obtained with mixtures of tung and linseed.

' Experiments 30 to 33 were conducted using an emulsion of lizseed oil and water in equal proportions. The break tees nus significantly better than that usually obtained linseed, but much poorer than that obtained with Bli -catalyzed linseed. The boil test values were, however. of the same order of magnitude as that obtained with rizturcs of tung and linseed.

Experimenl 34 to 39 were performed with Unitol BX (a refined grade of tall 00., manufactured by The Union 'were consistently below 5%, which were significantly matter of fact, polymerization with sulphur yielded postbake bond strength values much inferior to those obtained brushed on the overlay.

Bag-Camp Paper Corporation, New York, U.S.A.), both.

singly and mixed with linseed oil in equal proportions. When catalyzed with 10% BF -ether, Unitol BX showed excellent break tear values, but the boil test values were rather high (ZS-50%). However, this defect was remedied by using a 50:50 mixture of Unitol BX and linseed oil, catalyzed by 10% El -ether.

Experiments 40, 41 and 42 were the experiments with sulphur-polymerized linseed oil, and theresults obtained were very poor both in respect of out-of-press break tear" and the post-bake boil test. Both tests showed total peel. These experiments proved conclusively that polymerization by sulphur was no value in improving the bonding characteristics of drying oils, so far as the paper overlay hardboard process was concerned. As a with oils used without any polymerization aids.

Experiments 43 to 47 show the bonding character-' istics of maleinized oils. Experiment 43 used a maleinized linsed oil which was prepared in the laboratory and had a maleic anhydride content of 10%. ZymoF' and Varsoy" are commercially prepared (sold by Archer Daniels 7 (Midland), Canada Ltd.) rnaleinized linseed and maleinized soya oils. The viscosity of the maleinized oils were so high that they could not be sprayed but had to be In Experiments 46 and 47, a thinning hydrocarbon solvent was used to obtain spraying consistency. As the results show, maleinzation of the oils do not improve their overlay bonding capacity.

Experiments 51 to used bodied linseed as the bonding oil. The oil used in experiment 51 was prepared by heating linseed oil for 12 hours at 250 C. Experiments 52 to 55 used commercially bodied linseed oils. The high viscosity of these oils made direct spraying impossible and they had to be brushed on. In experiment 55, the bodied oil was thinned with a hydrocarbon solvent and then sprayed. The results indicate that bodying in the conventional sense does not improve overlay bonding characteristics of the oils. (The boil figures were actually higher with bodied oils than with plain oils.)

Xperiment 56 perhaps needs special mention. S0 is considered to be an excellent bodying catalyst for nonconjungated drying oils (such as linseed) as it is thought to introduce conjugated unsaturation in such oils via a proctss of isomerization. In experirg t 56, linseed oil saturated with S0 gas was used as the grinding oil. Once again, the data show that no improvement in bonding over pl lin linseed was obtained.

Exp. riments 57 to 60 show that the inclusion of the usual metallic driers in the oil, does not improve the bond. In these experiments Nuodex dn'ers were used in the recommended amounts.

The use of other FriedeLCrafts type catalysts, and in particular aluminum trichloride and stannic tetrachloride is shown in experiments 61 and 62. The reult how that The last three experiments in Table III show that BF;

can induce bonding characteristics in drying oils in atmospheres which are essentially non-oxidative, iii-sharp contrast to oils with no catalyst present. This agrees well with the fact that the El -catalyzed oils develop a fairly strong bond in the press (where little or no atmospheric oxygen is present}, whereas uncatalyzed' oils do not. 1

,h memnn.

The mtalyied oils containing the boron trifiuoride complexes were found to have the property of instantaneous gelation at a temperature of approximately 300 F. and

. e I t r perature in excess of about 300 F. to provide a hardboard with the paper overlay sheet consolidated with its surface, and baking the sheet of hardboard: said boron it is believai that in the press, when the temperature Fixes to a point substantially above this range, immediate gelation of the oil film on the board surface will occur.

I claim:

I. Artificiafi board comprising a hardboard base mat, a pape: overi'ay on at. least one surface of said hardboard base mat, said paper overlay being bonded to the Mse mat in tart by the natural bonding constituents of the base mat, a polymerized drying oil impregnated in said paper overlay and the adjacent surface of the base rnat providing an additional bond between the base mat and the paper overlay, and a boron trifiuoride catalyst incorporated in said drying oil in the amount of about two to ten percent: by weight of the drying oil; said drying oil being s lected from the group consisting of linseed oil; lung 03. and dehydrated castor oil. t

2. A promss for making an artificial board comprising tom-ting a partially dewatered base mat 'of wood fibres, said wood fibres being adhered together in the artificiai board at least partially by the natural bonding constituents of the base mat, applying a layer of drying oi} conzaining a boron trifiuoride catalyst to coat the surface of an overlay sheet of paper, applying the overlay sheet of paper to a surface of the base mat with the coated surface of the paper facing said surface of the base mat, pressing the mat and overlay sheet of paper at a temtrilluoride catalyst being present in the amount of about two to ten percent by weight of the drying oil; and said drying oil being selected from the group consistingof linseed oil, tung oil, and dehydrated castor oil.

3. A process as defined in claim 2, in which the mat and overlay sheet of paper are pressed at a temperature within the range 325 F.-385 F. t

7 References Cited by the Examiner UNITED STATES PATENTS 2,316,187 4/1943 Pratt et al. zed-407 I 2,441,t05 5/1948 Socolofsky et al 117 4t- 2,580,184 12/l95l Murray 106-252 2,918,398 12/1959 Dorland et al 162-}32 OTHER REFERENCES Cazes, Study of the Catalysis of Linseed Oil With Boron Fluoride Oleaginous, vol. 13, pp. 93 and 94, January 1958. 3 t

JACOB STEINBERG, Primary Examiner.

EARL M. BERGERT, ALEXANDER WYMAN,

Examiners.

W. F. ZAGURSKI, R. I. ROCHE,

Assistant Examiners. 

1. ARTIFICIAL BOARD COMPRISING A HARDBOARD BASE MAT, A PAPER OVERLAY ON AT LEAST ONE SURFACE OF SAID HARDBOARD BASE MAT, SAID PAPER OVERLAY BEING BONDED TO THE BASE MAT IN PART BY THE NATURAL BONDING CONSTITUENTS OF THE BASE MAT, A POLYMERIZED DRYING OIL IMPREGNATED IN SAID PAPER OVERLAY AND THE ADJACENT SURFACE OF THE BASE MAT PROVIDING AN ADDITIONAL BOND BETWEEN THE BASE MAT AND THE PAPER OVERLAY, AND A BORON TRIFLUORIDE CATALYST INCORPORATED IN SAID DRYING OIL IN THE AMOUNT OF ABOUT TWO TO TEN PERCENT BY WEIGHT OF THE DRYING OIL; SAID DRYING OIL BEING SELECTED FROM THE GROUP CONSISTING OF LINSEED OIL, TUNG OIL, AND DEHYDRATED CASTOR OIL. 